Image sensors have become ubiquitous. They are widely used in digital still cameras, cellular phones, security cameras, as well as, medical, automobile, and other applications. The technology used to manufacture image sensors has continued to advance at a great pace. For example, the demands of higher resolution and lower power consumption have encouraged the further miniaturization and integration of these devices.
The additional miniaturization has resulted in increased system integration, which has led to a need to avoid system level electromagnetic interference (EMI). Due, at least in part, to system integration, discrete crystal clock generation devices have been eliminated, and a system controller may generate the system clock in its place. An example clock generation circuit may be the phase locked loop (PLL) that is conventionally included in various electronics. However, clock signals generated by PLLs may not be as clean as clock signals generated by crystals leading to unwanted noise. The PLL generated clock signals may also cause, or add to, system EMI noise as well.
Many techniques have been employed to mitigate the effects of EMI noise, such as spread spectrum clocking. However, some of these methods may not entirely eliminate the effects of the noise and/or cause added system requirements, such as additional EMI shielding components.
Corresponding reference characters indicate corresponding components throughout the several views of the drawings. Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of various embodiments of the present invention. Also, common but well-understood elements that are useful or necessary in a commercially feasible embodiment are often not depicted in order to facilitate a less obstructed view of these various embodiments of the present invention.